McClintock ran for California's 36th State Assembly district in 1982 at the age of 26 after redistricting. He defeated Democrat Harriet Kosmo Henson 56%–44%.[3] In 1984, he won re-election to a second term, defeating Tom Jolicoeur 72%–28%.[4] In 1986, he won re-election to a third term, defeating Frank Nekimken 73%–25%.[5] In 1988, he won re-election to a fourth term, defeating George Webb II 70%–29%.[6] In 1990, he won re-election to a fifth term, defeating Ginny Connell 59%–36%.[7]

After running for Congress in 1992 and for controller in 1994, he decided to run for the Assembly again in 1996. He ran for California's 38th State Assembly district and defeated Democrat Jon Lauritzen 56%–40% to win his sixth assembly term.[8] In 1998, McClintock won re-election to a seventh term unopposed.[9]

In 2000, he decided to retire from the California Assembly to run for California's 19th State Senate district. He ranked first in the May 7th open primary with 52% of the vote. In November, he defeated Democrat Daniel Gonzalez 58%–42%.[12] In 2004, he won re-election to a second term, defeating Paul Joseph Graber 61%–39%.[13]

McClintock has a long history of opposing various tax increases. During the 2000 dot-com bubble, he was instrumental in proposing a two-thirds reduction in the vehicle license fee, or car tax. In 2003, he opposed then-Governor Gray Davis's attempt to rescind a rollback of a vehicle license fee.[14] McClintock has also opposed deficit reduction efforts that would have increased taxes. He supported the Bureaucracy Reduction and Closure Commission and performance-based budgeting.[15]

McClintock ran for State Controller again in 2002, facing Democratic nominee Steve Westly, an eBay executive. Westly outspent him 5-to-1. McClintock's campaigns focused on increasing accountability for the state budget. The ads featured the character Angus McClintock, a fictional cousin and fellow Scottish American extolling Tom McClintock's virtues of thriftiness and accountability with low-budget fifteen-second ads. He lost by a margin of just 0.2%, or 16,811 votes behind Westley, who won with a plurality of 45.3% of the vote. McClintock obtained 45.1% of the vote, while three other candidates obtained a combined 9.5% of the vote.[18]

In 2003, he ran for the recall election against incumbent Democrat Gray Davis. Film actor, Republican Arnold Schwarzenegger won the election 49% of the vote. DemocraticLieutenant GovernorCruz Bustamante finished second with 31% of the vote, which was about 17 points behind Schwarzenegger. McClintock finished in third place 14% of the vote, which was about 35 points behind Schwarzenegger. Together, Republicans Schwarzenegger and McClintock were supported by 5,363,778 Californians, or 62.1% of the vote. 132 other candidates obtained the remaining 6.4% of the vote.[19]

After redistricting, State Assemblyman McClintock decided to retire in order to challenge Democratic U.S. Congressman Anthony C. Beilenson in California's 24th congressional district. He won the nine-candidate Republican primary with a plurality of 34% of the vote, beating second-place finisher Sang Korman by eleven percentage points.[23] Beilenson defeated McClintock 56%–39%.[24]

On March 4, 2008, McClintock announced his candidacy for the U.S. House of Representatives in California's 4th congressional district, which is hundreds of miles away from the district McClintock represented in the state Senate. The district's nine-term incumbent, fellow Republican John Doolittle, decided to retire. McClintock was unable to vote for himself in either the primary or the general election because the California Constitution required him to maintain his legal residence in his State Senate district until the end of his Senate term. Furthermore, in order to vote using a ballot in regards to a specific congressional district, one must live within that district. Because Thousand Oaks is outside of California's Fourth Congressional District, McClintock was thus ineligible to vote for himself.[25]

Upon McClintock's entry into the race, fellow Republicans Rico Oller and Eric Egland withdrew from the Republican primary and endorsed McClintock.[25][26] McClintock was endorsed by the Republican Liberty Caucus,[27]Club for Growth, and U.S. Congressman Ron Paul. McClintock faced former U.S. Congressman Doug Ose, a moderate represented the neighboring 3rd District from 1999 to 2005. Ose lived outside the district and was painted as a carpetbagger and a liberal who had voted to raise taxes and who voted for earmarks. McClintock defeated Ose 54%–39%.[28]

The Democratic nominee was retired Air ForceLt. Col.Charlie Brown, who ran an unexpectedly strong race against Doolittle in 2006. In March 2008, Ose's campaign commercials criticized McClintock for receiving payments totaling over $300,000 in per diem living expenses during his time in the California State Senate, despite the fact that he lived in Elk Grove, near Sacramento, for most of the year. McClintock maintained that the payments were justified because his legal residence was in Thousand Oaks, in his State Senate district. He stated, "Every legislator's [Sacramento area] residence is close to the Capitol. My residential costs up here are much greater than the average legislator because my family is here."[29] However, Ose's campaign commercials argued McClintock does not own or rent in home in the 19th district, but uses his mother's address. These attacks prompted a response from McClintock's wife, Lori, who said McClintock stays with his mother in order to better care for her after she fell ill and after the death of her husband.[30] McClintock ran ads attacking Brown’s participation at a 2005 protest by Code Pink, an infamous anti-war group, and argued Brown supported gay marriage but not the troops in Iraq. He also portrayed Brown as a clone of SpeakerNancy Pelosi.[11]

By November 23, 2008, McClintock led Brown by 1,566 votes (0.4% of the vote), 184,190 to 182,624. Subsequent returns expanded the margin slightly with the last returns coming in from El Dorado County shortly after Thanksgiving. On December 1, 2008, McClintock declared victory and on December 3, 2008, Brown conceded the race. McClintock defeated Brown by a margin of 0.5%, or 1,800 votes. He prevailed by a 3,500-vote margin in Placer County, the largest county in the district. Brown won just three of the district's nine districts: Sierra (49.8%), Plumas (47.9%), and Nevada (42.3%).[31][32]

McClintock was challenged in the Republican primary again, this time by Michael Babich. He easily defeated Babich 78%–22%.[33] On November 2, he easily won re-election to a second term, defeating businessman Clint Curtis 61%–31%, winning all of the counties in the district.[34]

After redistricting, he decided to run in the newly redrawn 4th, which was moved significantly down the state. Only three counties remained from his prior district: Nevada, Placer, and El Dorado. Despite this, he easily won re-election to a third term, defeating Democrat Jack Uppal 61%–39%. He won all but two of the district's ten counties: Nevada (37%) and Alpine (41%).[35]

McClintock supported the Water Rights Protection Act, a bill that would prevent federal agencies from requiring certain entities to relinquish their water rights to the United States in order to use public lands.[40] The bill was a reaction to the United States Forest Service's decision to pursue a "new regulation to demand that water rights be transferred to the federal government as a condition for obtaining permits needed to operate 121 ski resorts that cross over federal lands."[41] McClintock supported the bill, saying that the Forest Service's regulation "illustrates an increasingly hostile attitude by this agency toward those who make productive use of our vast national forests, in this case by enhancing and attracting the tourism upon which our mountain communities depend."[41]